Depends on what you're doing. If you're upright, e.g. pressing/jerking, you want to be neutral. If you're pulling or squatting, you want to exaggerate the extension somewhat. The former because you're experiencing compression, and the latter because you're primarily resisting forward torque.

Hey Coach, Did you see my above post where I was noting that I wasn't trying to make this a Verstegan vs. Everett thread but those were just the two books I had in the library on the subject....

Just playing devils advocate at this point...so based on your notes above, is hollowing out acceptable for a press or jerk. One of my observations above was that the hollowing out and activating the TA seemed to promote a more neutral spine position, for myself at least...